1. Field of the Invention
This invention relates to magnetic recording disks and more particularly, to such disks having a capacitive servo pattern therein for use with a track following servo system.
2. Description of the Prior Art
Magnetic recording disk files have for a number of years employed some type of track following servo system to maintain one or more magnetic heads properly centered over a selected one of a plurality of concentric data recording tracks on a disk surface. Some disk files (usually larger capacity files) used one disk surface which contained the track following servo information and hence was dedicated to servo purposes. The major drawback to such dedicated servo surfaces is that they are necessarily positioned some distance from the data-containing surfaces in the disk file so that mechanical misalignment of the disks or magnetic heads can lead to errors in track following ability. This is a particular problem with the trend in disk files for higher and higher track densities with the concomitant demand for higher performance servo systems.
Other commercial disk files employ a so-called sector servo in which the track following servo information is stored in sectors which are interspersed around the disk surface between data portions. This approach has the advantage that the servo information is stored on the same surface as the data tracks which are to be followed by the servo system, but it has the disadvantage that the disk surface area devoted to the servo information results in a decrease in disk surface area available for data storage.
An approach which appears very attractive for servo systems is the so-called embedded servo in which the track following servo information is placed in the data disk--either in, below or above the data-containing layer--without reducing the data storage capacity of the data surface.